The present invention relates to tank pressure control systems, and particularly, to apparatus for regulating discharge of liquid fuel and fuel vapor from a fuel tank. More particularly, the present invention relates to tank venting control apparatus that closes quickly and automatically at the proper moment to prevent discharge of agitated liquid fuel from the tank and overfill of the tank.
During vehicle cornering and dynamics, the liquid fuel inside a vehicle fuel tank is often agitated to cause the liquid fuel to move with a splashing motion inside the vehicle fuel tank. Liquid fuel can also be sloshed about in a vehicle fuel tank in response to other types of vehicle motion in addition to vehicle cornering.
Vehicle fuel tanks include vent apparatus for regulating discharge of liquid fuel and fuel vapor from the interior region of the fuel tank. Such a vent apparatus is often mounted in an aperture formed in a top wall of the vehicle fuel tank and could be exposed to agitated liquid fuel that is sloshed about inside the vehicle fuel tank during cornering or other movement of the vehicle.
According to the present invention, a tank vent control system includes a valve container and a valve movable in an interior chamber formed in the valve container to open and close a chamber outlet formed in the valve container. The valve regulates flow and discharge of pressurized fuel vapor admitted into the interior chamber through a chamber inlet coupled to a vehicle fuel tank. In an opened position of the valve, an exterior wall of the valve cooperates with an interior wall of the valve container to define a vent passage to conduct pressurized fuel vapor through the interior chamber from the chamber inlet to the chamber outlet. In a closed position of the valve, an outlet closure included in the valve is positioned to close the chamber outlet.
As the valve is moved upwardly in the interior chamber due to rising liquid fuel levels and/or tilting of the valve container, the valve reaches a xe2x80x9csnap-closure positionxe2x80x9d located between the opened and closed positions. At this point, the exterior wall of the valve engages an upper interior wall defining a boundary of the interior chamber to partition the interior chamber into a lower region communicating with the chamber inlet and containing pressurized fuel vapor from the vehicle fuel tank and an upper region communicating with the atmosphere through the chamber outlet. Once the interior chamber is partitioned, a xe2x80x9cpressure differentialxe2x80x9d is established between the lower and upper regions owing to admission of pressurized fuel vapor (from the fuel tank) into the lower region and development of relatively low-pressure atmospheric conditions (from the atmosphere) in the vented upper region. A xe2x80x9clifting forcexe2x80x9d is applied to the valve as a result of this pressure differential to assist in moving the valve quickly from the snap-closure position to the closed position while the pressure extant in the lower region of the interior chamber is higher than the pressure extant in the upper region of the interior chamber.
Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.